Removed unnecessary overloads of Future::after.
Removed unnecessary overloads of Future::after.

Review: https://reviews.apache.org/r/29536

kaysoky/mesos,abudnik/mesos,chhsia0/mesos,asamerh4/mesos,verizonlabs/mesos,zmalik/mesos,Aman-Jain-14/customizedMesos,chhsia0/mesos,verizonlabs/mesos,gsantovena/mesos,yuquanshan/customizedMesos,kaysoky/mesos,reneploetz/mesos,zmalik/mesos,neilconway/mesos,jpeach/mesos,craimbert/mesos,kaysoky/mesos,asamerh4/mesos,dforsyth/mesos,kaysoky/mesos,reneploetz/mesos,abudnik/mesos,reneploetz/mesos,asamerh4/mesos,neilconway/mesos,gsantovena/mesos,abudnik/mesos,andschwa/mesos,neilconway/mesos,dforsyth/mesos,asamerh4/mesos,andschwa/mesos,Gilbert88/mesos,yuquanshan/customizedMesos,Gilbert88/mesos,abudnik/mesos,verizonlabs/mesos,abudnik/mesos,gsantovena/mesos,dforsyth/mesos,abudnik/mesos,gsantovena/mesos,verizonlabs/mesos,andschwa/mesos,chhsia0/mesos,Gilbert88/mesos,yuquanshan/customizedMesos,Gilbert88/mesos,craimbert/mesos,verizonlabs/mesos,craimbert/mesos,neilconway/mesos,yuquanshan/customizedMesos,asamerh4/mesos,neilconway/mesos,Aman-Jain-14/customizedMesos,dforsyth/mesos,Gilbert88/mesos,jpeach/mesos,zmalik/mesos,reneploetz/mesos,dforsyth/mesos,chhsia0/mesos,gsantovena/mesos,reneploetz/mesos,chhsia0/mesos,Aman-Jain-14/customizedMesos,jpeach/mesos,kaysoky/mesos,zmalik/mesos,craimbert/mesos,jpeach/mesos,reneploetz/mesos,kaysoky/mesos,chhsia0/mesos,yuquanshan/customizedMesos,yuquanshan/customizedMesos,andschwa/mesos,gsantovena/mesos,zmalik/mesos,zmalik/mesos,andschwa/mesos,verizonlabs/mesos,yuquanshan/customizedMesos,Gilbert88/mesos,Gilbert88/mesos,craimbert/mesos,craimbert/mesos,Aman-Jain-14/customizedMesos,chhsia0/mesos,andschwa/mesos,jpeach/mesos,dforsyth/mesos,gsantovena/mesos,Aman-Jain-14/customizedMesos,Aman-Jain-14/customizedMesos,Aman-Jain-14/customizedMesos,neilconway/mesos,abudnik/mesos,zmalik/mesos,verizonlabs/mesos,asamerh4/mesos,andschwa/mesos,jpeach/mesos,reneploetz/mesos,kaysoky/mesos,craimbert/mesos,dforsyth/mesos,neilconway/mesos,jpeach/mesos,asamerh4/mesos